MP/H Rules/Histology--Colon: What histology would be coded when the right colon demonstrates a combined adenocarcinoma and high grade small cell neuroendocrine carcinoma [forming the dominant component] arising in a villotubular adenoma and the liver biopsy demonstrates metastatic high grade small cell neuroendocrine carcinoma?
For cases diagnosed 2007 or later, start with rule H1 in the Single Tumor module. Stop at rule H4. Assign code 8263 [adenocarcinoma in tubulovillous adenoma].
Stop at the first rule that applies. Code histology based on a specimen from the primary site whenever available.
MP/H Rules/Histology--Breast: What histology code for a diagnosis of pleomorphic lobular carcinoma in situ?
For cases diagnosed 2007 or later, code the histology as lobular carcinoma, in situ [8520/2].
The steps used to arrive at this decision are:
Open the Multiple Primary and Histology Coding Rules Manual. Choose one of the three formats (i.e., flowchart, matrix or text). Go to the Breast Histo rules because site specific rules exist for this primary.
Start at the SINGLE TUMOR: IN SITU CARCINOMA ONLY module, Rule H1. The rules are intended to be reviewed in consecutive order. Stop at the first rule that applies to the case you are processing. Code the histology to lobular carcinoma in situ [8520/2] because this is the only histologic type identified.
Pleomorphic lobular carcinoma is a variant of lobular carcinoma which does not have an ICD-O-3 code. It is still a lobular carcinoma. The identification of the variants of lobular carcinoma was a relatively recent discovery and the information was not available when the 2007 MP/H Rules were written. All of the lobular variants will be included in the next revision of the MP/H Rules.
Tumor Size/Bladder: The 2018 SEER Coding and Staging Manual says to use imaging over physical exam as priority for determining tumor size. If a bladder tumor is 4 cm visualized on cystoscopy, and is 2.8 cm on CT scan, which should be used as the clinical size? Is cystoscopy (endoscopy) a clinical exam or imaging?
For the case described here, use the size from the CT scan. Physical exam includes what can be seen by a clinician either directly or through a scope. A tumor size obtained visually via cystoscopy is part of a physical exam. Therefore, the imaging (CT) tumor size is preferred. Use text fields to describe the details.
MP/H Rules/HistologyCorpus Uteri: How should histology be coded for a "carcinosarcoma with high grade sarcomatous component within a polyp, with greater component of endometrioid carcinoma and foci papillary serous carcinoma within polyp"?
For cases diagnosed 2007 or later, assign code 8980/3 [Carcinosarcoma] according to rule H17. Rule H12 does not apply since the final diagnosis is not "adenocarcinoma."
Reportability--Brain and CNS: Are hemangioma, NOS (9120/0), cavernous hemangioma (9121/0) or venous hemangioma (9122/0) reportable when they arise in the brain or CNS?
Hemangioma, NOS (9120/0) and cavernous hemangioma (9121/0) arising in the dura and parenchyma of the brain/CNS are reportable.
Venous angiomas (9122/0) are not reportable wherever they arise. The primary site for venous hemangioma arising in the brain is blood vessel (C490). The combination of 9122/0 and C490 is not reportable. This is a venous abnormality. Previously called venous angiomas, these are currently referred to as a developmental venous anomalies (DVA).
MP/H Rules--Colon: What histology would you assign to a single tumor with the histology 'well differentiated mucinous cystadenocarcinoma in a villous adenoma confined to the appendix'? Does rule H4 apply to this diagnosis or should we continue on in the rules to H14 and code the higher histology?
For cases diagnosed 2007 or later, use rule H4.
Stop at the first rule that applies to the case. Rule H4 is the first rule that applies.
The polyp rule, H4, comes before many of the other colon rules because it is important to know that the malignancy originated in a polyp.
Histology--Heme & Lymphoid Neoplasms: How is this field coded for a patient with a negative bone marrow and multiple plasmacytomas in different bone sites (e.g., thoracic vertebrae and left femur)?
Updated May 2026
The original answer for this question was to code the primary site to C419 [Bone, NOS] and histology to 9731/3 [solitary plasmacytoma]
In 2021, we received clinical guidance from the WHO 4th edition which stated the presence of two plasmacytomas is multiple myeloma (9732/3), even if the bone marrow is negative or not evaluated. Registrars were not required to go back and review older cases.
This case would be coded as a single primary, 9732/3 and primary site C421.
Computed Ethnicity: Should the Name--Alias field be used when generating Computed Ethnicity?
No, "Alias" is not used and should not be used to generate Computed Ethnicity. Computed Ethnicity records the ethnicity based on last name and/or maiden name using a computer algorithm. Alias is not part of the algorithm.
Multiple Primaries (Pre-2007): Whenever two hollow organs are diagnosed simultaneously with the same histology, one being invasive and the other in situ, can one assume that mucosal spread has occurred and that this situation represents one primary? In the absence of a physician statement, how do you determine mucosal spread from one organ to another?
For tumors diagnosed prior to 2007:
Yes, this type of situation represents one primary. A tumor that is breaking down can be invasive in the center with in situ cancer at the margins. Occasionally the in situ margin can move into a contiguous organ with the same type of epithelium.
Physicians may describe mucosal spread in various manners. You will see the terms "intramucosal extension," "in situ component extending to," or statements of an invasive component in one organ, with adjacent/associated in situ carcinoma in a contiguous organ with the same type of epithelium. A frequent example of this process is bladder cancer extending into the prostatic urethra via mucosal spread.
For tumors diagnosed 2007 or later, refer to the MP/H rules. If there are still questions about how this type of tumor should be coded, submit a new question to SINQ and include the difficulties you are encountering in applying the MP/H rules.
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